Probably the most important part of my kitchen is the large jar of salt by my cooker, an ever present reminder to season lightly, but season often. I'm assisted in this discipline in that the jar has a very shallow spice spoon, capacity probably just under 1/2 a teaspoon, which makes it very difficult to over-salt a dish and forces me to come back every so often.
To flavour a dish with salt properly, it is essential to appreciate that it is best transferred into whatever you are cooking via absorption of the liquid or stock. Take two dishes, say rice. One is cooked without salt and the salt sprinkled on afterwards. The other dish is cooked in salted water. The second dish will taste considerably better, as the salt will be distributed evenly throughout. The other dish will be bland and tasteless with the occasional burst of flavour.
So what I tend to do is to lightly season at every stage of the cooking process, tasting as I go. Frying some onions? Add a touch of salt. Adding some chicken? Make sure it is seasoned before it goes in the pan or season it as it is added. Obviously, you don't want to taste the uncooked chicken, but you get the idea. Whenever you add ingredients, it then becomes second nature. Just remember to add a little seasoning at each stage
What is important though is to realise that some ingredients are more "Salt tolerant" than others. Potatoes and rice for instance, will require more seasoning than bacon or olives. You will pick this up with experience, but if you season lightly and frequently, tasting as you go along, you will not go far wrong and your dish will be well balanced and flavourful.
As one chef once commented (I can't remember who), it is totally unforgivable not to taste a dish for seasoning prior to serving. That is the very least one can do, even if you have forgotten or skipped seasoning throughout the cooking process.